There's a lot of ~~normal~~ people who follow the President in the same way they follow...The Rock or Demi Lovato. It's actually a pretty normal early behavior in joining a social network! It's why the account is a public good. https://twitter.com/jeneps/status/1349918380678139904
Sure, plenty of rando bots and trolls, but also, plenty of folks who don't really engage in politics. Plenty of hate follows. Who knows! It's why Twitter moved the followers over from Obama to Trump! It's not a political account, it's the President's account.
Anyway, the nice thing about Joe Biden is that he truly couldn't care less about Twitter followers. Or Twitter! But he does care about communicating with everyone in the country, whether they agree with him or not.